The Cross Island Line (CRL) will be the longest line in Singapore’s MRT network at more than 50 kilometres long upon its completion in the 2040s. As part of this large-scale infrastructure development, the 350-metre long and 47-metre deep Pasir Ris Interchange Station located along Pasir Ris Drive 1 will be one of the deepest underground stations in the country.
The five-level underground interchange station that links up CRL, CRL-Punggol Extension (CPe) and East-West Line (EWL) is set to open in 2030, serving the residential and industrial areas in Loyang; Tampines; Pasir Ris; Hougang; Serangoon North; and Ang Mo Kio.
ENHANCED SUPPORT SYSTEMS TO ENSURE SAFE CONSTRUCTION
The station will be built by a top-down construction method with the use of permanent slabs as an excavation support system. Temporary struts and walers as well as cross-walls have been applied to further enhance the excavation support system and minimise impact to surrounding structures. Diaphragm walls have also been introduced to act as a retaining system to effectively facilitate underground excavation and construction.
The construction work in this phase also involves addition and alteration works to the existing Pasir Ris station along the EWL, as well as new cut and cover (C&C) tunnels to the west and east of the station to serve two tracks of CRL (eastbound and westbound) and CPe (northbound and southbound). Part of the east tunnel will be used as a launching shaft of a tunnel boring machine for the construction of a twin bored tunnel connecting Pasir Ris Interchange Station and Pasir Ris East Station.
SITE CONSTRAINTS AND CHALLENGES
The area where the CRL Pasir Ris Interchange Station meets the EWL caused space constraints, requiring specialised equipment such as a low-headroom mobile crane to be deployed for the construction of diaphragm walls. The design team has also adopted the over-cutting method for the diaphragm wall joints, in lieu of the conventional water-stop plate method, to overcome the limited space constraints.
Soil condition is another concern. There is a small stretch of Kallang formation (loose stratum consisting of sand, gravel and sticky clay with boulders overlying) at the site, which is susceptible to settlement. Given the potential unexpected ground conditions with highly variable soil parameters, extensive site investigations including soil and water tests were conducted during the design stage. The team also applied Plaxis 3D geotechnical modelling software to analyse ground behaviour in order to better understand the sub-surface soil conditions and design robust earth retaining systems.
SUSTAINABLE AND LONG LIFESPAN
The station is planned with five entrances. Each entrance is designed with green roof and solar panels, as well as perforated glass façade to facilitate natural ventilation and daylight. To promote comfortable and healthy indoor environment, materials with low carbon, toxic and volatile organic compound (VOC) emissions certified by Singapore Green Building Council have been chosen for the station. These are in line with the Building and Construction Authority’s efforts to encourage sustainable construction.
All permanent work structures are designed for a lifespan of 120 years with appropriate maintenance strategies during the operation period.—Construction+ Online
Cross Island Line Pasir Ris Interchange Station (Phase 1)
Pasir Ris, Singapore
Status of Construction
Site substructure construction in progress
Station Gross Floor Area
81,925.7 square metres
47 metres deep
Land Transport Authority (LTA), Singapore
Lead Design Consultant
Aurecon Singapore (Pte) Ltd
Principal Consulting Engineers
Khalid Mahmood; Er Dr Ravi Prasad; Er Marcus Tong
ONG&ONG Pte Ltd
Wendy Tan Kuan Kuan; Wang Lai Meng
Design & Build Contractor
Daewoo Engineering & Construction – Dongah Geological Engineering Singapore Branch Joint Venture (DDJV)
ONG & ONG